Warp knit fabric



March 4, 1969 s. L. PORTER ETA!- 3,430,465

WARP KNIT FABRIC Original Filed Feb. 26, 1959 United States Patent M 7 Claims ABSTRACT OF THE DISCLOSURE A lightweight, soft fabric which conforms readily to contoured surfaces and is characterized by a pinning strength in excess of about 2 pounds, hence is well adapted for utility as a sanitary napkin cover fabric, comprising a plurality of sets of continuous filament cellulose acetate yarns knit into an open construction characterized by less than full set threading in the chain yarns, and a stitch pattern in the transversel extending yarns at least several needle spaces wide.

This application is a continuation of application Serial No. 508,609 filed August 5, 1965 now abandoned, which in turn is a division of copending application Serial No. 795,858 filed February 26, 1959, now US. Patent No. 3,208,451.

The present invention relates to warp-knit fabrics.

It is an object of the present invention to provide fabrics which are soft, light in weight, strong and easy and inexpensive to produce.

It is a further object of the invention to provide a fabric having the properties described which conforms readily to contoured shapes without bunching or wrinkling.

Another object of the invention is to provide an open fabric which will permit the ready passage of liquid therethrough without excessive wicking.

Still another object of the invention is the provision of fabric coverings for sanitary napkins, for non-woven articles, of decorative ribbons, and the like.

Other objects and advantages of the invention will become apparent from the following detailed description and claims.

In accordance with one aspect of the invention there is provided a warp-knit fabric of open construction weighing less than about 1, and preferably less than about 0.8,

ounce per square yard. The fabric is especially suited for use as the outer covering of sanitary napkins and particularly of contoured or shaped sanitary napkins in which end use the ability of the fabric to conform without bunching and attendant discomfort is most advantageous.

For such end use, thev fabric is preferably knit of continuous filament yarns since in that manner the necessary strength can be achieved at low deniers, low deniers being softest. The denier of the yarns generally is less than about 150 and preferably less than about 125 but usually at least 10 denier. Advantageously the fabric is knit on a double bar machine, the yarns of one bar forming longitudinally extending chains to lock the essentially transversely extending yarns of the other bar into predeter- Patented Mar. 4, 1969 ICC mined position in forming the fabric. Because of the loopformation of the yarns in forming the chains, these chains exhibit increased strength and advantageously may be made of yarns of less than about denier. The transversely extending yarns, however, while preferably below about denier are desirably of somewhat higher denier than the chain yarns.

Advantageously the individual filaments of the yarns are less than about 20 and preferably less than about 5 denier since the lower deniers are softer. The chemical composition of the yarns may var widely and, for example, may constitute rayon, nylon, polyesters such as polyethylene terephthalate, polymers and/or 'copolymers of olefins or vinyls such as ethylene, propylene, vinyl chloride, vinylidene chloride, acrylonitrile, and the like. Preferably, however, the yarns comprise organic acid esters of cellulose such as the lower alkanoic acid esters, e.g. cellulose acetate. Cellulose acetate is desirable because of its softness, its inertness, and its balance of hydrophilic and hydrophobic properties, i.e. a material will not be suitable which is so hydrophobic as to resist penetration of aqueous fluids or so hydrophilic that it will wick up the fluid rather than permitting the fluid to pass into deeper layers of the napkin intended for absorbency.

Another advantage of cellulose acetate is that it can easily be adhered to the substrate without stiffening, e.g. as by spraying the substrate lightly with a solvent such as acetone, a plasticizer such as triethyl citrate, or the like. Most important, cellulose acetate is less expensive than other continuous filamentary materials of comparable low denier.

The fabric when used for sanitary napkins should have a pinning strength, defined more fully hereinafter, in excess of about 2 and preferably .in excess of about 2.5 pounds. The pinning strength will depend upon the yarn denier and the fabric construction. A satisfactory construction has been found to involve yarns On one bar of a double bar warp-knitter which yarns span just one needle and form chains, e.g. the bar may be threaded 1 in 2 out and the stitch pattern will be l-O, O-l. The yarns of the other bar are the transversely extending yarns; these may span several needles and may be knitted to adjacent transversely extending yarns on one or both sides by the chain yarns of the first bar. This, of course, will depend upon the threading and stitch pattern. Alternatively, each of the transversely extending yarns may be knitted to only chain yarns and to no adjacent transversely extending yarn, being merely looped, not positively knitted to adjacent transversely extending yarns; this makes for more rapid machine operation and for production of a softer fabric still exhibiting adequate strength.

Where multifilament yarns are employed the filaments are generally twisted together to permit processing on the knitting machine. Advantageously there are 10 or fewer turns per inch and preferably 1 or fewer turns per inch since low twist yarns, while less expensive, give softer fabrics and more cover than high twist yarns.

In addition to their use as coverings for sanitary napkins, the novel fabrics can be employed wherever low weight fabrics are desired. Thus they can constitute a backing or scrim in place of gauze for non-Wovens such as filters, battings used in making quilted fabrics, and the like. Alternatively, they may be made in narrow widths and used as decorative lace-work ribbons alone or in conjunction with plastic films, etc.

In connection with variations in the Width of the fabric in end use applications, the use of warp-knit fabrics presents certain additional advantages. Thus the knitting machine may be made to produce in full width and by appropriate omission of certain warp yarns several fabrics of less than full machine Width. As compared with having to produce narrower widths by cutting a wide fabric, the invention avoids uneven edges with fiber strands and shreds. Alternatively, the fabric may be produced in full width and by absence of locking between adjacent warps it may neatly be subdivided into several fabrics of lesser width.

for forming a sanitary napkin. The layers comprise three sheets of tissue paper 17, a web of viscose fiber 18, two sheets of tissue paper 19, a layer of wood pulp fiber 20, a sheet of water repellent tissue 21, four sheets of tissue 22, another layer of wood pulp fiber 23, another sheet of tissue 24, eight sheets of tissue 25 and a cover layer 26. In accordance with the present invention this cover layer 26 is constituted by a warp knit fabric of the construction shown in FIGS. 1 and 2.

The following table illustrates several satisfactory fabric constructions, employing cellulose acetate continuous filament yarns twisted to the extent of about 1 turn per inch:

Example N 1 2 3 4 5 6 7 8 9 Stitch Pattern, Fig 2 2 2 1 2 1 2 1 1 Chain Yarns, Denier/File" 55/22 55/22 55/22 55/22 55/22 .55/22 55/15 55/15 55/15 Transverse Yarns, Denier/F s 75/20 75/50 75/50 75/50 75/20 75/20 55/15 75/20 55/15 Wales/Inch 21 21 28 28 28 28 28 28 28 Courses/Inch" 17 23 23 28 23 28 21 28 44 Fabric Weight, ounces/sq. yd 0. 64 0. 67 0. 67 0.8 0. 67 0. 8 0. 67 0.8 0. 9 Inches/Rack (480 Courses) 28 21 21 17 21 17 23 17 11 Inches of Chain Yarns Fed/Rack 94 70 70 60 7O 60 74 64 58 Inches of Transverse Yarns Fed/Rack- 120 100 100 46 100 46 100 48 44 Pinning Strength, lbs 3. 6 3. 5 3.1 2. 8 2. 4

As contrasted with circular knit fabrics, the war knit fabrics are free from curling at the edges and they are easily handled during wrapping about the napkin pad due to their low stretch in the longitudinal direction. The high stretch in the transverse direction still permits wrinklefree accommodation to various shaped articles with good contact between the fabric and article, which is desirable in permitting capillary flow through to the article.

The novel fabrics properties cannot be duplicated by weaving. Thus continuous filament yarns when woven tend to slide over one another, especially when subjected to stress as in pulling on a pin, and result in a dimensionally unstable fabric. This sliding tendency can be overcome by bonding but this stiffens the fabric rendering it uncomfortable. If staple fiber yarns are substituted for continuous filament yarns, the lesser strength will necessitate the use of heavier deniers, coarser yarns and coarser constructions.

The invention will be further described with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic illustration of the construction of one fabric;

FIG. 2 is a diagrammatic illustration of the construction of a second fabric; and

FIG. 3 is an elevation of a sanitary napkin immediately prior to wrapping of the cover layer thereabout.

Referring now more particularly to the drawings, in FIG. 1 there is shown a fabric comprising warp yarns 11 formed into longitudinally extending chains and other warp yarns 12 formed into essentially transversely extending yarns. The dots 13 represent the needle positions and from the figure it can be seen that the bar carrying yarns 11 is threaded 1 in 2 out with a 1-0, O-l stitch pattern while the bar carrying yarns 12 is threaded 1 in 1 out 1 in 3 out with a 0-0, 5-5 stitch pattern.

In the fabric illustrated in FIG. 2, the positions of needles 14 show that the bar carrying chain-forming warp yarns 15 is threaded 1 in 2 out with a l0, 0l stitch pattern while the bar carrying transversely extending warp yarns 16 is threaded 1 in 2 out with a stitch pattern of 3-4, l-O. It will be seen that the laterally projecting loops of each wale are not knotted to the projecting loops of adjacent wales; instead the loops of each Wale fit loosely into the adjacent loop (not shown, but apparent from the shorthand illustration). Consequently the wales can be separated from one another, if desired, to produce fabrics of predetermined width. Advantageously, at least every twentieth, e.g. every tenth transverse yarn is not knotted to one or both of the adjacent transverse yarns so as to permit severing into fabrics of whatever width desired. Alternatively by omission of selected warp yarns several fabrics of predetermined width can be simultaneously produced without slitting.

FIG. 3 shows the stacked pad layers plus cover layer The pinning strength was determined by clamping one end of a fabric sample between a pair of jaws mounted at a fixed location on a rod. Another pair of jaws was mounted on a carriage capable of sliding along the rod; the second pair of jaws had two L-shaped pins projecting therefrom and spaced one-half inch laterally from one another. The pins extended toward the first pair of jaws and then stuck up through the fabric. A weight was mounted on the second pair of jaws and the rod was tilted to vary the tension on the fabric, the fabric wales running parallel to the rod. The pinning strength is the vector of the weight acting along the rod when the pins tore the fabric. Any other tensile testing machine meeting ASTM D7653 requirements, suitably modified with pins, can be similarly employed.

EXAMPLE 10 Another sample was prepared generally similar to Sample 1 but differing therefrom in the stitch pattern. Thus the chain yarn bar was threaded 2 in 2 out-1 in 2 out, 1 in 3 out (71X), 2 in 1 out, starting with the first guide on the bar. The back bar was also threaded starting with the first guide, 1 in 2 out (74X)2 out. This produced a 7 inch wide fabric with selvages, making a neater appearing fabric. In addition it eliminated break-outs which otherwise occurred at the edges, and thereby increased the production speed. In other respects the fabric was the same as that produced in Example 1.

The products of Examples 1 and 10 are all-around the best from the standpoints of low weight, high pinning strength, softness, satisfactory appearance and balance between hydrophobic and hydrophilic properties. The fabrics provide suflicient cover for the encased layers so :as not to appear too flimsy; at the same time even though the cover layers exert no action on fluids placed thereon they are sufliciently open and have many pores of adequate size to permit viscous fluids to be wicked up by the substrata of the napkins.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A warp knit fabric of a plurality of sets of continuous filament cellulose acetate yarns, said fabric comprising a plurality of longitudinally extending chain yarns holding together a plurality of essentially transversely extending yarns, said yarns being knit into an open construction which imparts to said fabric a low stretch walewise and a high stretch course-wise, the chain yarns having a denier of about 10 to about 75, being threaded no more fully than 1 in, 2 out, and being knit in a stitch pattern of l0, O1, the transversely extending yarns having a denier of about 10 to about 100 and being knit in a stitch pattern at least several needle spaces wide, said transversely extending yarns being of higher denier than said chain yarns, said fabric having a weight of less than about one ounce per square yard, :and a pinning strength in excess of about 2 pounds.

2. The warp knit fabric of claim 1, said yarns comprising individual filaments having a denier of less than about 20, being twisted together less than about 10 turns per inch.

3. The warp knit fabric of claim 1, said fabric having a weight of less than about 0.8 oz./yd.

4. A warp knit fabric according to claim 1, wherein the transversely extending yarns are knit into a stitch pattern of 3-4, 1-0.

5. A warp knit fabric according to claim 4, wherein said transversely extending yarns are threaded 1 in, 2 out.

6. A warp knit fabric according to claim 1, wherein said transversely extending yarns are knit into a stitch pattern of 00, 5-5.

7. A warp knit according to claim 6, wherein said transversely extending yarns :are threaded 1 in, 1 out, 1 in, 3 out.

References Cited UNITED STATES PATENTS 2,142,908 1/ 1939 Mendel. 2,433,279 12/1947 Johnson. 2,535,376 12/1950 Thompson. 2,711,168 6/1955 Brickman et al. 2,845,783 8/1958 Underwood et al. 3,208,451 9/1965 Porter et al.

FOREIGN PATENTS 787,949 12/1957 Great Britain. 803,787 10/ 1958 Great Britain.

ROBERT R. MACKEY, Primary Examiner. 

